text: Various kits have a 93 to 95% sensitivity (true positive rate). For hospitalized patients, one study found the specificity to be about 50% (related to false positive rate) in the diagnosis of thrombotic disease.
  * False positive readings can be due to various causes: liver disease, high rheumatoid factor, inflammation, malignancy, trauma, pregnancy, recent surgery as well as advanced age.
  * False negative readings can occur if the sample is taken either too early after thrombus formation or if testing is delayed for several days. Additionally, the presence of anti-coagulation can render the test negative because it prevents thrombus extension. The anti-coagulation medications dabigatran and rivaroxaban decrease D-dimer levels but do not interfere with the D-dimer assay.
  * False values may be obtained if the specimen collection tube is not sufficiently filled (false low value if underfilled and false high value if overfilled). This is due to the dilutional effect of the anticoagulant (the blood must be collected in a 9:1 blood to anticoagulant ratio).
  * Likelihood ratios are derived from sensitivity and specificity to adjust pretest probability.
  In interpretation of the D-dimer, for patients over age 50, a value of (patient's age) × 10 μg/L may be abnormal.